One difference in a hydraulic oil filter vs an engine oil filter is the filtering capability of the filter paper. Today's hydraulic oil filters have a micron rating of 10 microns. One micron equal 1/2500 of an inch. Most engine oil lifter have a rating of 25 to 40 microns. This means the hydraulci oil filter will remove finer particles and become plugged up faster in engine oil. Finer particles need to be removed from teh hydraulci oil due to the much higher pressures seen in a hydraulic system 2000 - 25000 psi vs 1015 psi in an engine oil system. The other thing you need to verify does the hydraulic filter have an internal by pass valve as do most engine oil filters and at what pressure does it open.

As Edward T said leave the old engine filter on. I would add, also drain and replace engine oil. At least you have @ 4 to 4.5 quarts of clean oil in the engine mixed with a pint of dirty oil.